Question

Consider recent clinical results using electric fields to disrupt rapidly dividing tumor cells. When cells are dividing, some elements of the cell develop a small net charge, and others develop a dipole structure with a positive charge on one end and a negative charge on the other. When a uniform electric field is applied to the body, the field will not be uniform inside the body. The motion of charges and polarization effects, both of which vary strongly from place to place, create a field that is quite variable at the level of the cell. The field is strong in some places and weak in others. The varying field exerts forces and torques on the cell components. This can disrupt cell division, which can have an especially large impact on the rapidly dividing cells in a tumor. To illustrate this idea, we consider a cylindrical element with a dipole structure but no net charge, embedded in a dividing cell. The varying environment of the cell creates a local variation in the strength of the field. The field and the dipole element are shown in the figure (Figure 1).

Part A

The element will rotate into a position in which the net torque is zero. Once the element is in this position, the net force is directed 

• to the left 

• to the right

Describe the motion of this element. 

Drag the terms on the left to the appropriate blanks on the right to complete the sentences. 

Answer 1